Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It discloses that the tool returns all holders, lists slot names, and deliberately omits values—a key behavioral trait. It is a read-only operation by implication ('Returns'), and no side effects are mentioned. This is adequate for a simple index tool, though it doesn't mention ordering or pagination, which could be minor gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single sentence with no redundancy. It front-loads the core action ('Returns every holder'), specifies the resource, and adds the essential qualifier about values. Every word earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a parameterless tool with no output schema, the description completely specifies what is returned and what is not. The sibling tools (locker_get, locker_put) naturally follow from the context, and no further information is needed for an agent to decide whether to call this tool. The description is sufficient for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero parameters, so the schema imposes no burden. The description adequately describes the outcome (a list of holders and slot names) without needing to explain parameters. A baseline of 4 is appropriate for parameterless tools that clearly state their behavior.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('Returns') and a clear resource ('every holder with a locker and the names of their slots'), and explicitly notes what is omitted ('without the values'). This distinguishes it from sibling tools like locker_get and locker_put, which deal with values, making the purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage context: use this to get an overview of all lockers and slot names, not their contents. While it doesn't explicitly name alternatives, the 'without the values' qualifier signals that value retrieval would require a different tool (e.g., locker_get). This is clear context without explicit exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.